The Myth of Swing Voters in Midterm Elections

By Lynn Vavreck

April 22, 2014

If you want to understand the 2014 midterm elections, remember this simple fact about American politics: There just aren’t that many swing voters.

Many people change their minds over the course of a campaign about whether to vote and even which candidate they’re leaning toward. Ultimately, though, voters tend to come home to their favored party. There are relatively few voters who cross back and forth between the parties during a campaign or even between elections.

Political professionals have increasingly come to appreciate this pattern and have focused resources on getting previous voters to the polls. Both parties have spent considerable effort in recent elections trying to understand the effects of television ads, canvassing, phone calls and mailings on turnout. Mobilizing a party’s voters has become as important as persuading undecided or swing voters.

The 2010 midterm elections highlight the relatively small number of swing voters. After winning with a wide margin and extraordinary enthusiasm in 2008, the Democrats suffered one of the largest losses of seats in any midterm two years later.

Although the president’s party almost always loses seats in midterm elections, the size of the 2010 “shellacking,” to borrow President Obama’s description, created the impression that many voters had changed their minds about the president, his policy goals or his ability to get the country back on the right track between 2008 and 2010.

But only a small percentage of voters actually switched sides between 2008 and 2010. Moreover, there were almost as many John McCain voters who voted for a Democratic House candidate in 2010 as there were Obama voters who shifted the other way. That may be a surprise to some, but it comes from one of the largest longitudinal study of voters, YouGov’s Cooperative Campaign Analysis Project (C.C.A.P.), for which YouGov interviewed 45,000 people at multiple points during 2011 and 2012.

The results clearly show that voters in 2010 did not abandon the Democrats for the other side, but they did forsake the party in another important way: Many stayed home.

Fewer than 6 percent of 2008 voters in the presidential election voted for a congressional candidate from the other party in 2010, with the switchers roughly evenly divided across the parties, according to the C.C.A.P. It’s worth noting, however, that these switchers are not evenly distributed around the country, with North Dakota’s single district having very few cross-party voters (under 3 percent) and some Pennsylvania districts, for example, having upward of 10 percent switching between 2008 and 2010.

On average, across districts, roughly 6 percent of Obama voters switched and just under 6 percent of McCain voters switched; because there were more Obama voters than McCain voters in 2008, this means — as you’d expect — that more voters swung to the Republicans than to the Democrats. An additional 1.5 percent switched to third-party candidates.

But on turnout, the numbers were not evenly balanced for Democrats and Republicans. Only 65 percent of Obama’s 2008 supporters stuck with the party in 2010 and voted for a Democrat in the House. The remaining 28 percent of Mr. Obama’s voters took the midterm election off. By comparison, only 17 percent of McCain’s voters from 2008 sat out the midterms.

Turnout in midterm elections is always down from presidential elections, and Democrats routinely fight to return more of their voters to the polls than the Republicans. More Democrats come from groups, such as young people and Latinos, that typically vote at lower rates in midterm elections than other groups. But this 11-point difference in holding on to 2008 voters is larger than normal. It probably stemmed from a gap in enthusiasm between the parties’ voters in 2010, as survey data indicated.

It may seem hard to believe that the shellacking was more about who turned up than about who changed their minds between 2008 and 2010, but it lines up with a lot of other evidence about voters’ behavior. Most identify with the same political party their entire adult lives, even if they do not formally register with it. They almost always vote for the presidential candidate from that party, and they rarely vote for one party for president and the other one for Congress. And most voters are also much less likely to vote in midterm elections than in presidential contests.

These stable patterns of American politics reveal a clear path for both parties in 2014: Get your 2012 voters to the polls. Of concern to Democrats right now is that Republicans once again have the upper hand on enthusiasm going into November.